Effect of Zn Vacancies in Zn₃In₂S₆ Nanosheets on Boosting Photocatalytic N₂ Fixation

Abstract

Photocatalytic nitrogen fixation is considered as a very promising technology to solve the high-energy consumption problem in industrial ammonia synthesis. Because of the mildness of reaction conditions, its development is still limited by the low reaction efficiency and unknown reaction mechanism. Inspired by the mechanism of biological nitrogen fixation in nature, Zn 3 In 2 S 6 with different sulfur sources is prepared to study the effects of cation defects on the adsorption, activation, and reaction in photocatalytic nitrogen fixation. Because of the electron-rich property of zinc vacancies in Zn 3 In 2 S 6 nanosheets, it can effectively activate the NN triple bond, thereby increasing the rate of kinetic reduction. With the activation of N 2 molecules on zinc vacancies, the existing protons obtained from methanol (solvent) will greatly accelerate the electron transfer between interfaces during the nitrogen reduction reaction. Notably, Zn 3 In 2 S 6 with rich Zn vacancies exhibits higher activity (355.2 mg L −1 g cat −1 , 15 times) than Zn 3 In 2 S 6 with poor vacancies in nitrogen fixation. This work describes the contribution of zinc vacancies to the fixation and activation of nitrogen molecules, which is very important to establish a highly effective system of photocatalytic nitrogen fixation.

Few-Layer ZnIn2S4/Laponite Heterostructures: Role of Mg2+ Leaching in Zn Defect Formation

“…The partial replacement of Zn by Mg caused distortion of the crystalline lattice of ZnIn 2 S 4 , in particular, compression in the (102), (110), and (202) crystalline planes shown by XRD measurements. Introducing such zinc vacancies in ZnIn 2 S 4 layers that serve as electron capture centers would enhance charge separation efficiency. , Due to the formation of few-layer-thick lamellae and the occurrence of Zn defects, the photophysical properties of ZIS-Lap samples are effectively adjusted, giving rise to enhanced transient photocurrent and photocatalytic degradation of methyl orange compared with ZnIn 2 S 4 . These enhancements were shown to result from increased light absorption and enhanced charge transport capabilities of few-layered ZnIn 2 S 4 .…”

Boosting Nitrogen Activation via Bimetallic Organic Frameworks for Photocatalytic Ammonia Synthesis

“…On one hand, the electron transfer from N 2 to the metal (process 1) could be fortified by pulling two lone pair electrons at both ends of N 2 . On the other hand, the electron transfer from the metal to N 2 (process 2) could be promoted by some methods, e.g., fabricating surface defects, constructing heterojunctions, and forming localized surface plasmon resonance fields. , However, processes 1 and 2 are two opposite and strongly coupled electron-transfer processes, making them in a “trade-off” dilemma and directly resulting in a high potential activation energy barrier and low photocatalytic activity . Coordinating these two processes requires concurrently strong electron acceptance and donation capacity of the active sites, which is hardly highly efficiently achieved by the monometallic catalyst.…”

A minireview on catalysts for photocatalytic N2 fixation to synthesize ammonia

“…For instance, Zn decient Zn 3 In 2 S 6 exhibited a NH 3 generation rate of 261.2 mmol g À1 h À1 under visible light irradiation, 15 times higher than the one with poor defects. 45 (3) On some defective semiconductors, the defective sites not only improve light harvesting capacity but also facilitate N 2 activation. For example, Bi 2 WO 6 hollow microspheres prepared by a solvothermal template-free method are rich in oxygen vacancies.…”

“…For instance, Zn deficient Zn 3 In 2 S 6 exhibited a NH 3 generation rate of 261.2 μmol g −1 h −1 under visible light irradiation, 15 times higher than the one with poor defects. 45 …”